The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to a disk drive base of the HDA. The HDA includes at least one disk, a spindle motor for rotating the disk, and a head stack assembly (HSA). The PCBA includes a disk controller for generating servo control signals. The HSA includes a head for reading and writing data from and to the disk. The HSA is controllably positioned in response to the generated servo control signals from the disk controller to move the head relative to tracks of the disk.
The HSA includes an actuator assembly, at least one head gimbal assembly (HGA), and a flex cable assembly. The actuator assembly typically includes an actuator having an actuator body with one or more actuator arms extending from the actuator body. Each actuator arm supports the HGA that includes a head. An actuator coil is supported by the actuator body. The actuator coil interacts with a magnet to form a voice coil motor. The PCBA controls current passing through the actuator coil that results in a torque being applied to the actuator. The HSA further includes the flex cable assembly in electrical communication with the PCBA. The flex cable assembly supplies current to the coil and carries signals between the head and the PCBA.
A flexure extends along the load beam and is considered a sub-component of the HGA. The head includes a slider and a transducer disposed on the slider. The head is attached and electrically connected to the flexure. The flexure includes a flexure tail portion that extends away from the head. The flexure tail portion is disposed adjacent the actuator body and attaches with the flex cable assembly. The flexure includes conductive traces that extend from adjacent the head and terminate in the flexure tail portion. The flex cable assembly includes a flex cable that connects with the flexure tail portion.
The flexure further includes a dielectric layer and a metal backing layer. The metal backing layer is typically formed of stainless steel. The conductive traces are formed upon the dielectric layer which insulates the traces from electrically shorting via the metal backing layer. The flexure further includes a tongue portion that structurally supports the head. First and second gimbal arms extend between the tongue portion and the flexure body portion. The gimbal arms and the tongue portion are generally referred to as a gimbal of the flexure.
In practice the thermal and hydroscopic expansion coefficients are quite different among the conductive traces, the dielectric layer, and the metal backing layer. Such differences can result in stresses and strains developing within the gimbal of the flexure due to its laminated nature. In this way, the differences in coefficients can lead to increased pitch static attitude (PSA) sensitivity to temperature and humidity changes in the disk drive. As such, it is desirable that the contributions of the conductive traces and dielectric layer to the gimbal stiffness (Kp) be minimized so as to reduce the thermal and hydroscopic effect upon PSA of the flexure.
Prior art gimbal designs have included the use of discrete separated sections of the dielectric layer so as to create discontinuities in the overall laminate flexure structure. This approach has found success in reducing the pitch static attitude (PSA) sensitivity to temperature and humidity changes of the flexure. However, another gimbal design requirement is robustness with regard to ultra-sonic activated aqueous (AQ) cleaning processes. Where multiple discrete sections of the dielectric layer are used, the conductive traces at locations where there are discontinuities between discrete sections of the dielectric layer have been found to be susceptible to damage during such cleaning processes.
As such, there is a need in the art for an improved flexure gimbal design approach with a relatively reduced pitch static attitude (PSA) sensitivity to temperature and humidity changes of the flexure while having adequate structurally robustness with regard to ultra-sonic activated aqueous (AQ) cleaning processes.